A massive stretch of bladderwrack seaweed in the Baltic Sea has just been revealed as one of nature’s biggest surprises. For years, scientists assumed it was a diverse population of marine plants, but a groundbreaking study has uncovered the truth—it’s actually a single, giant clone that has spread across 310 miles (500 kilometers) of ocean. This discovery, published in Molecular Ecology, makes it one of the largest known genetic clones on Earth.
A Seaweed Clone Like No Other
Scientists initially believed the algae belonged to a species called narrow wrack, a common type of seaweed found in the Bothnian Sea, a northern part of the Baltic. However, after conducting genetic tests, researchers from the University of Gothenburg were stunned to find that it was actually common bladderwrack—but with a crucial difference.
This particular bladderwrack doesn’t rely on sexual reproduction like most of its kind. Instead, it clones itself, with fragments of the original female plant drifting through the water, settling, and growing into genetically identical copies. Over time, these clones have formed an underwater forest so vast that it dominates some areas of the Baltic.
“This clone comprises millions of individuals, and in some areas, it is completely dominant ,” said Ricardo Pereyra, a marine scientist at the University of Gothenburg who led the genetic analysis. “We have found a few more large clones in the Baltic Sea, but the female clone off the Swedish Gulf of Bothnia is by far the largest—a real super female.”
An Essential Part Of The Marine Ecosystem
Bladderwrack plays a crucial role in the Baltic Sea’s marine environment. It forms dense underwater forests that serve as nurseries for young fish, snails, crustaceans, and other marine species. These habitats provide shelter, food, and protection from predators.
However, while this enormous clone has successfully expanded its range, its genetic uniformity poses a serious risk. Unlike sexually reproducing populations, which mix genes to create variation, clones are genetically identical.
The Hidden Danger Of Genetic Uniformity
“A clone almost completely lacks the genetic variation that otherwise means that there are individuals in a population that can handle the changes and make the species survive.” explained Kerstin Johannesson, a biologist at the University of Gothenburg and co-lead author of the study.
Genetic diversity is crucial for adaptation. In a population with many genetic differences, some individuals may have traits that help them survive disease, pollution, or temperature changes. If one group is vulnerable, others may persist and pass on their resilience.
But in a clonal population, if a single disease, parasite, or environmental shift threatens one individual, it threatens them all.
What This Discovery Means For Science?
This finding raises fascinating questions about marine plant evolution and survival. How did this super female clone spread so far? How long has it existed? And are there even larger clones waiting to be discovered in the world’s oceans?
The study published in Journal Molecular Ecology also identified a closely related seaweed species in the same region—one that reproduces sexually rather than cloning itself. This contrast raises new mysteries about why some species favor one reproductive strategy over another.
Understanding the advantages and weaknesses of clonal expansion could help scientists predict how marine ecosystems will respond to climate change and guide conservation efforts to protect fragile underwater habitats.
